Weed control by two cover crops Neonotonia wightii and Centrosema pascuorum in banana plantations - impact on nitrogen competition and banana productivity

Intercropping bananas with cover crops is a promising alternative to chemical weed control. In this study, we evaluated two legume species Neonotonia wightii (NW) and Centrosema pascuorum (CP) for their weed control ability in a banana plantation. The impact of these living covers on soil nitrogen content and on banana productivity was also evaluated in comparison to a spontaneous weed cover (SP) and to a chemical weed control (CWC). For the three treatments with a living cover, a grass-specific herbicide was applied at 60 days after planting, and mowing was performed at 120 days after planting. At crop emergence, NW and CP showed similar above-ground biomass per plant; thereafter the higher biomass growth rate of CP resulted in a higher covering ability. At 90 days after planting, CP had a biomass of 6 t ha(-1) dry matter (DM), and resulted in a 55% weed biomass reduction in comparison to SP. CP growth declined after this stage, and there was no regrowth after mowing. NW produced only 1 t ha(-1) DM at 90 days after planting and provided no weed control at this stage. NW showed a good regrowth 240 days after planting, after the mowing provided a 60% reduction of weed biomass in comparison to SP. Nevertheless, NW and CP did not reduce the global nitrogen uptake of the cover in comparison to SP, and demonstrated a negative effect similar to that of SP on soil mineral nitrogen content compared to CWC. Both cover crops reduced the banana leaf emission rate and pseudostem girth by 24% in comparison to CWC at 131 days after planting. NW and CP did not impact the bunch weight but delayed the flowering date by 5 weeks, in comparison to CWC, which corresponded to 10% of loss in the crop productivity per year.